Amazon.com Inc. is offering to pass along the discounts it gets on credit-card fees to other retailers if they use its online payments service, according to people with knowledge of the matter, in a new threat to PayPal Holdings Inc. and card-issuing banks.

Amazon has all the infrastructure from a payments perspective to immediately begin competing in the space (logistics, payments, brand, marketing, distribution, etc). However, key concern for any merchant that has success on Amazon's platform is at what point does Amazon enter that business themselves (e.g. everything Amazon is doing with Amazon basics).